Beginning the 15th of June 2016 and for the seventh day in a row the rains have come down in the tropics of the Riviera Nayarit. It only rains at night which works well into many people’s schedule; however… it is curious that the rain only falls at night. With an inquisitive mind I decided to do some research.
During the day the sun beats down and the humidity grows at an alarming rate. Late in the day, high above the mountains you can see clouds growing to a bilious height. By early evening the thunder can be heard, off in the distance, but… definitely headed toward the flat land of the coast.
Some types of precipitation are diurnally affected, such as thunderstorms that result from surface heating. These storms usually form in the afternoon, and may extend well into the nighttime, before dissipating in the early morning. (1)
During the day, the sun aids in the evaporation of excess moisture in the air. At night, there is no sun, so excess moisture builds up in the clouds and dumps rain at night. The humidity is very high and you can almost feel the water rising from the hot ground up into the waiting sky above where clouds form.
Warm air holds more water molecules than cooler air. When temperatures lower at night, relative humidity tends to increase because the air cannot hold more moisture. It eventually reaches the dew point (where the temp = dew point or basically 100% relative humidity). Between 90-100% relative humidity, you’ll start seeing ‘fog’ or just the water in the air. So… because cooler air cannot hold as much moisture, and it cools off at night, you’ll encounter precipitation at night more often than during the day.
Well now I know why the humidity increases during the day to the point that I think I am going to faint just before the life saving rain comes falling down. And I thought Mother Nature was just having fun with us.
This information is not to be confused with the large storms brought to us by passing hurricanes. Those are different and definitely requiring other research.
The following video is short reminder on how the process works here on earth.